High frequency collecting and radiating structure



June 23, 1936. M. P. HANSON 2,044,779

HIGH FREQUENCY COLLECTING AND RADIATING STRUCTURE Filed April 8, 71955 3 Sheets-Sheet l INVENTOR ATTORNEY June 23, 1936. M, P; HANSON 2,044,779

HIGH FREQUENCY COLLECTING AND RADIATING STRUCTURE Filed April 8, 1955 5 Sheets-Sheet 2 INVENTOR ATTORNEY um 23, 1930 M. P. HANSON 2,044,779

HIGH FREQUENCY COLLECTING AND RADIATING STRUCTURE Filed April '8, 1933 5 Sheets-Sheet 3 I INVENTOR BY M/Qflvhsa);

ATTORNEY Patented June 23, 1936 UNITED STATES PATENT OFFICE HIGH FREQUENCY COLLECTING AND RADIATING STRUCTURE (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757).

My invention relates to the direct and practical utilization of the metallic structures of air, water or land-borne craft for the radiation and collection of electromagnetic Waves having a frequency whose corresponding half wave length approaches the physical dimensions of such structures as may be used. It more particularly relates to the utilization of airplane structures for the above purposes. a

An object of my invention is to provide a means of radio communication which will obviate the necessity of using any trailing wire or exteriorly exposed antenna system.

Another object of myinvention is to provide a means for simultaneous two-Way radio communication by coupling a radio transmitter to the structure so as to set up oscillations in one direction, for example fore and aft, and simultaneously employing a radio receiver coupled so as to respond to oscillations in another direction, such as wing to wing or transverse, thus balancing out the effect of the transmitter upon the receiver.

Other objects of my invention and the invention itself will become more apparent by reference to the following description, in which description reference will be had to the accompanying drawings forming a part of this specification.

In all prior systems for' the employment of radio equipment aboard an airplane it has been customary to. use the structure of the plane as the ground or counterpoise andv a separate antenna system. The method I have employed is particularly useful where the so-called superhigh frequencies are to be used. With these frequencies, it has been. found that no external antenna is necessary, it being sufficient merely to connect one side of the transmitter output to one portion of the airplane fuselage while the other side of the transmitter output is connected to another portion ofthe airplane fuselage. At

' tion and then the other by the oscillating transmitter and a portion of this energy being radiated in the form of electromagnetic waves. As may be seen from the above, the same principle can be applied to the reception of radio signals on aircraft.

An airplane may have different resonance frequencies when oscillating in a fore-and-aft direction or when oscillating laterally. In one case, the metallic fuselage carries the main portion, of the radio frequency current, while in the other case the metal framework or bonding of the wings serves as the oscillating structure. Any of the hereinafter described coupling methods may of course be thus applied to excite either fuselage, wing structure or any other portion capable of individual oscillation.

A great variety of electrical coupling methods may be employed to transfer electrical oscillations between a metallic portion of an airplane or similar structure and a radio transmitter or receiver. In many cases, choice of some particular method will be dictated by such factors as frequency employed, structural connection, size and shape of the structure or location of radio equipment within the structure. of oscillation set up may be simple transverse, simple longitudinal, complex transverse, complex longitudinal or multiphase. Most of the methods suggested appear efiicient only for frequencies such that the dimensions of the oscillating structures approach one-half wave length of the frequency used, or the structure may be set into harmonic oscillations at still higher frequencies. An exact relationship between frequency used and structural dimension need not expressly be maintained, especially for the higher frequencies. Referring to the drawings:

Figs. 1 to 7 inclusive show various schematic arrangements of a radio transmitter and electrical couplings in a system of radio communication utilizing a portion of an aircraft as radi ators of electromagnetic energy;

Figs. 8 to 10 inclusive illustrate diagrammatic equivalent electrical circuits of the arrangements shown in. Figs. 1 to 3, inclusive.

Referring to the different figures of the drawings in all of which like parts are designated by like reference characters, and in which are disclosed methods of coupling a radio transmitter to various metallic structures, Fig. 1 shows one end of the output coupling coil of a self-contained transmitter T connected by a conductor G to an exposed metal member in the extreme after part of the fuselage, while the other end 7 of the output coil is connected to the shielding case surrounding the transmitter. This shielding structure is to be understood as being entirely insulated from the fuselage. Reduced to its simplest form, the equivalent circuit is shown The type in Fig. 8, where L is the transmitter output coupling coil, C the effective capacitance of the transmitter shielding case to the adjacent plane structure, and AB a conductor approximately the length of the fuselage. While the effect of the wings and other transverse or vertical members is not represented in the simple diagram, it is evident that the metallic structure AB, even with added portions representing the wings and tail surfaces, may be set into oscillation by conductive coupling through its portion DE which is in common with the circuit, LDEC, energized by the transmitter T. While C may consist merely of the capacitance of the transmitter case to the fuselage, the insertion of an actual condenser at C of various values may give improved performance, depending upon the characteristics of the airplane structure, frequency used, length and nature of coupling DE and self-inductance and magnetic coupling to transmitter of output coil L.

i Fig. 9 illustrates a modification of the coupling methods shown in Figs. 1 and 8, wherein a relatively non-radiating two-wire feed line is used. For the most practicable results, distance LF should approximate an odd number of quarter Wave lengths of the frequency employed.

Fig. 2 shows a method of coupling the transmitter to the airplane wing structure by capacitative relation to a dipole suspended closely adjacent the structure. By means of this arrangement, the length of the metallic wing AB may be set into oscillation by the capacitative relations existing between AB and DE. In using wing structures, it must be understood that the electrical bonding between wing sections be positive. In this method, due to the capacity effects used, length DE is not intended, or necessary, to be harmonically related to length AB or the frequency employed.

Fig. 3 illustrates the excitation of a structure by a double feeder line, connected at points some distance apart. Coupling is thus effected at the current anti-node by the self-inductance and distributed capacitance of section DE which is common to both linking circuit and radiating system. The equivalent circuit is shown in Fig. 10.

Figs. 4, 6 and '7 show the application of an electromagnetic loop radiator or collector for producing electrostatic displacement suitable for radiation from a metallic structure. In effect, this represents a loop circuit in which the periodic current emerges from one end of a feed wire on the inside of the structure, connects to and spreads over the outside of the radiating object, traverses its length before again concentrating and returning into the internal conductor at the other end. This method is particularly applicable where the structure is to radiate frequencies at or below its fundamental frequency. Fig. '7 shows the case where, at the fundamental frequency, when the distance AB is approximately one-half wave length, the combined capacitative reactance of the feeder system is adjusted to be equal to its inductive reactance between points A and B. This, in effect, places the oscillating system inside the structure in parallel with that of the structure itself, thereby readily exciting it into oscillation and radiation. In this case, the greatest potential difference in the system would exist between points A and B. For communication on' frequencies below this fundamental, the greatest potential difference exists between C1 and C2, as shown in Figs. 4

and 6, and the structure with its internal feeder acts more nearly like a concentric loop. Sufficient difierence of potential exists between points A and B, however, to set up radiation and provide communication over a limited distance. It should be noted that the small arrows in Figs. 4 and 6 indicate instantaneous current flow in the case where AB is less than one-half wave length, whereas in Fig. 7 they represent instantaneous conditions when AB is of resonant length.

Fig. 5 illustrates the possibility of multiphase excitation of the typical airplane structure. In this case, three-phase excitation is indicated,

the three radiating members being specifically the right and left-hand wings and fuselage-tail structure. This, of course, would require a suitable three-phase oscillator, coupled to L1, L2 and L3. The advantage of such a multi-phase oscillation would consist in a reduction of directional radiating properties and decrease of fading. Other multi-phase arrangements are possible, such as two-phase oscillation of the forward and after parts of the fuselage together with the right and left portions of the wings. Any of the previously described coupling methods might be employed for exciting the individual portions of the structure in this manner.

In the above figures which illustrate some possible coupling methods, the transmitter as indicated by T in all cases may be replaced by a. receiving apparatus. While all the drawings indicate inductive coupling between T and the energy transfer circuits, other coupling methods, such as capacitative or resistive, may be employed. Furthermore, the circuits linking the transmitter or receiver to the structure may be either tuned or untuned, as the introduction of inductances and/or condensers in the coupling system does not alter the principle involved.

While I have described certain preferred embodiments of my invention, I desire that it be understood that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims. I desire it further understood that while the application of my invention has been described principally in connection with aircraft, it is not so limited and may be extended to many other types of continuous, self-contained metallic structures, such as dirigibles, submarines and surface vessels, automotive vehicles, etc.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon.

What I claim is:

1. In a system of radio communication, a radio transmitter mounted entirely within and insulated from an airplane consisting in part of metal, an output coil operatively connected to said transmitter, a shield surrounding said transmitter, means connecting one end of said coil to said shield, means connecting the other end of said coil by a single conductor to an exposed structural metallic member in the tail of said airplane whereby a longitudinal portion of the metallic parts of said airplane may be utilized as a radiator of electromagnetic energy at a frequency whose half-wave length corresponds approximately to the length of the fuselage of said airplane.

2. In a system of radio communication, a radio receiver mounted within and insulated from an airplane consisting in part of metal, an input coil operatively connected to said receiver, a shield surrounding said receiver, means connecting one end of said coil to said shield, means connecting the other end of said coil to an exposed structural metallic member in the tail of said airplane whereby a longitudinal portion of the metallic parts of said airplane may be utilized as a collector of electromagnetic energy at a frequency whose half-wave length corresponds approximately to the length of the fuselage of said airplane.

3. In combination, an aircraft consisting in part of metal, radio apparatus mounted within and insulated from said aircraft, an energy transfer coil operatively connected to said radio apparatus, a shield surrounding said radio apparatus, means connecting one end of said coil to said shield, means connecting the other end of said coil to a structural metallic member of said aircraft at a point displaced from the center thereof whereby a portion of the metallic parts of said aircraft may be utilized as a radiator or collector of electromagnetic energy of a frequency whose half-wave length corresponds approximately to the length of a selected dimension of said aircraft.

MALCOLM P. HANSON. 

